Relatives of some of the 16 preachers from a moderate Muslim sect who were allegedly killed by Malian soldiers in a “barbaric massacre” went to the presidential palace in Mauritania’s capital Monday to find out why the men were gunned down.

NOUAKCHOTT, MAURITANIA—Relatives of some of the 16 preachers from a moderate Muslim sect who were allegedly killed by Malian soldiers in a “barbaric massacre” went to the presidential palace in Mauritania’s capital Monday to find out why the men were gunned down.

The preachers from the moderate Dawa sect, some of whom were from Mauritania, were stopped Saturday night at a checkpoint in the central Malian town of Diabaly and shot dead by the Malian military overnight, according to relatives of the dead and the Mauritanian government. The men had been on their way to a religious conference in the Malian capital.

“They had no arms on them. ... This is a group of Muslims who were preaching the just cause of Islam, and were far from extremists. They wanted to use Islam to reach a political end without violence,” said Hanena Ould Abdallahi, a relative of one of the victims.

The circumstances remain murky, but reports suggest that the long-bearded preachers were mistaken for the radical Muslim group which seized control of the northern Mali earlier this year. Last week, the jihadists pushed south and took over the town of Douentza in a move that has left the Malian army jittery and on edge. But Diabaly is well-within the area under government control, and there is no indication that the preachers were armed.

In a statement published Monday, Mauritania’s Minister of Foreign Affairs described the killing as “an indescribable criminal act, committed in cold blood without any warning against preachers who were armed with nothing more than their faith. Mauritania also called it a “barbaric massacre” and an “odious crime,” underscoring the rising tension between the two nations which have previously been partners in their fight against Islamic terrorism.

Mali’s government has opened an investigation and sent a high-ranking delegation to Mauritania. A government communique said: “An incident occurred on the night of Saturday, Sept. 8, 2012 at the security checkpoint in Diabaly, in which 16 people were subsequently killed. They include eight Malians and eight Mauritanians, who were killed by bullets.” The statement stopped short of saying that Malian soldiers had carried out the killing.

Parents, brothers and cousins of the dead gathered Monday in front of the presidential palace in Mauritania’s capital, Nouakchott, begging for answers.

Abdallahi and other relatives said the preachers are from the so-called Dawa sect of Islam, considered moderate.

“Why did they kill them? That is the question,” said Zeine Ould Mohamed Lamine, whose three cousins are among the dead.

“We don’t understand. They left for Mali, they had all the necessary paperwork. They didn’t do anything fraudulent. They were travelling by the main highway,” he said. “Why did this happen?”